Pedestrians, such as a walking person, may not notice an approaching hybrid vehicle or an electric vehicle, which moves very quietly. Various types of approaching vehicle warning speaker devices are proposed to be mounted on a vehicle, such as a hybrid vehicle, to generate a warning sound to notice pedestrians of an approaching vehicle, such as a hybrid vehicle. Manufacturers independently determine specifications of such approaching vehicle warning speaker devices. So that, approaching vehicle warning speaker devices are not designed based on unified standards specifying, for example, thermal resistance or environmental resistance.
The trend in recent years has shown that the method of mounting the approaching vehicle warning speaker device and the specification of the approaching vehicle warning speaker device are to be legislated. Furthermore, the approaching vehicle warning speaker device, which is mounted near an engine or a motor in a hybrid vehicle or the like, is required to have environmental resistance, such as the reproduced sound pressure, thermal resistance, moisture resistance, and water resistance for each frequency band.
One of objects of the present invention is to raise the high reproduced sound pressure and to improve environmental resistance such as thermal resistance, moisture resistance, and water resistance.